Synthesis method of solid electrolyte and carbon composite-coated lithium-rich manganese-based cathode material

Abstract

The present invention belongs to the technical field of secondary battery materials. More specifically, it relates to a synthesis method of a solid electrolyte and carbon composite-coated lithium-rich manganese-based cathode material. The method of the present invention includes: first, mixing anhydrous ethanol and glycerol evenly, then adding aluminum nitrate and conductive carbon, ultrasonically dispersing evenly, and then adding the lithium-rich manganese-based material, heating and stirring to concentrate to obtain a concentrated material; after calcining the concentrated material, cooling to obtain a calcined material; ultrasonically reacting the calcined material with a strong base solution, washing with water, and drying to obtain a carbon-coated lithium-rich manganese-based material; mixing and dispersing the carbon-coated lithium-rich manganese-based material and water; dissolving lithium hydroxide in water to obtain a lithium hydroxide solution; adding titanium sulfate, lanthanum nitrate, and chromium sulfate to water to dissolve to obtain a mixed solution; adding the mixed solution to the main material suspension, after mixing, adding the lithium hydroxide solution, reacting, filtering, drying, and then performing a high-temperature reaction, discharging to obtain the solid electrolyte and carbon composite-coated lithium-rich manganese-based cathode material.

Description

Technical Field

[0001] The present invention belongs to the technical field of secondary battery materials. More specifically, it relates to a synthesis method of a solid electrolyte and carbon composite-coated lithium-rich manganese-based cathode material. Background Art

[0002] The lithium-rich manganese-based cathode material is a cathode material for lithium-ion batteries with high energy density potential. It is considered a strong candidate for the next-generation lithium-ion battery cathode material due to its high specific capacity, low cost, and environmental friendliness.

[0003] Compared with traditional lithium iron phosphate materials or lithium nickel cobalt manganese oxide materials, the lithium-rich manganese-based material has a higher working voltage, which can reach 4.5V or even higher. The reason for the relatively high working voltage of the lithium-rich manganese-based cathode material is mainly related to its unique electrochemical activity. This material can be regarded as composed of two components, Li2MnO3 and LiMO2. Within 4.5V, the valence of nickel and cobalt in the conventional layered structure LiMO2 increases, and at the same time, lithium ions in the conventional layered structure are deintercalated from the cathode and inserted into the anode, and some lithium ions in the Li2MnO3 layer also deintercalate and enter the layered structure. The new plateau that appears above 4.5V is attributed to the contribution of the electrochemical activity of the Li2MnO3 layer at high voltages, including the valence change of part of the manganese, the loss of part of the structural oxygen as oxygen and the formation of oxygen vacancies, the loss of electrons of -2 valence oxygen to become -1 valence oxygen to provide charge compensation, the deintercalation of lithium ions from the transition metal layer to form Li2O and the rearrangement of the material structure into a conventional layered structure, and the complex charge compensation relationship among lithium, manganese, and oxygen. This unique electrochemical activity and charge compensation mechanism enable the lithium-rich manganese-based cathode material to work at a higher voltage, thus providing a higher working voltage.

[0004] However, for the lithium-rich manganese-based material, the material itself has low ionic / electronic conductivity, so it exhibits poor rate performance. The rate performance of the lithium-rich manganese-based cathode material is closely related to its kinetic characteristics, including the Li+ ion diffusion rate of the material itself and the transfer rate at the electrode / electrolyte interface. The low intrinsic diffusion coefficient of lithium ions in the Li2MnO3 phase in the lithium-rich manganese-based cathode material also severely restricts its rate performance. Therefore, how to improve the rate performance of the material at the raw material level is one of the technical problems faced by those skilled in the art. Summary of the Invention

[0005] The technical problem to be solved by the present invention is as follows: for the lithium-rich manganese-based material prepared by traditional processes, its ionic conductivity and electronic conductivity are relatively low. Although it can be improved by means such as surface coating, the inventors have found that due to the expansion and contraction stresses existing inside the battery during long-term cycling, the continuous presence of such stresses will cause the coating layer on the surface of the material to be prone to cracking and peeling during long-term cycling, thereby leading to serious attenuation of battery performance and the product service life cannot be effectively guaranteed. Based on the above problems, the present invention provides a synthesis method for a solid electrolyte and carbon composite-coated lithium-rich manganese-based cathode material.

[0006] The object of the present invention is to provide a synthesis method for a solid electrolyte and carbon composite-coated lithium-rich manganese-based cathode material.

[0007] The above object of the present invention is achieved by the following technical solutions:

[0008] A synthesis method for a solid electrolyte and carbon composite-coated lithium-rich manganese-based cathode material, the specific synthesis steps include:

[0009] Coating the lithium-rich manganese-based material with an island-like distributed carbon composite layer:

[0010] By weight, take 100 - 120 parts of absolute ethanol, 4 - 6 parts of glycerol, 4 - 6 parts of aluminum nitrate, 0.4 - 0.6 part of conductive carbon, and 38 - 45 parts of lithium-rich manganese-based material;

[0011] First, mix absolute ethanol and glycerol evenly, then add aluminum nitrate, stir to dissolve it, add conductive carbon, disperse it evenly by ultrasonic wave, and then add the lithium-rich manganese-based material, heat and stir to concentrate to volatilize the absolute ethanol to obtain a concentrated material;

[0012] In the above steps, with absolute ethanol as the main solvent and supplemented with a certain amount of glycerol component, first, under the action of absolute ethanol, aluminum nitrate dissolves, and during the concentration process, the aluminum-containing component gradually deposits on the surface of the lithium-rich manganese-based material. During this deposition process, thanks to the presence of a small amount of glycerol component, both the aluminum-containing component and the conductive carbon can obtain a more uniform deposition effect. This is mainly because glycerol has a higher boiling point compared to ethanol. Therefore, after the rapid evaporation of ethanol, it can still provide a certain amount of fluidity required on the deposition surface;

[0013] Transfer the concentrated material into a carbonization furnace, under the protection of nitrogen, at a temperature of 500 - 550 °C, continuously calcine for 4 - 6 h, then cool and discharge to obtain a calcined material;

[0014] In the carbonization furnace, under high-temperature conditions, glycerol further volatilizes or decomposes and will not remain in the system, while the aluminum-containing component decomposes to form an alumina component, and together with conductive carbon, a uniform deposition layer is formed on the surface of the lithium-rich manganese-based material. Due to the decomposition of the aluminum-containing component and the volatilization or decomposition of glycerol, gases can be generated, and the diffusion of the gases causes the deposition layer to form a porous structure;

[0015] The calcined material is ultrasonically reacted with a strong alkali solution, washed with water, and dried to obtain the carbon-coated lithium-rich manganese-based material;

[0016] On the premise of the existence of the aforementioned porous structure, under the action of ultrasound, the strong alkali solution diffuses and penetrates into the pores. In this way, most of the exposed alumina can be eroded and dissolved by the strong alkali solution. During this process, the part co-coated with the dissolved alumina detaches from the surface of the lithium-rich manganese-based material, thereby forming an island-shaped coating layer on the lithium-rich manganese-based material. The part that is not dissolved by the strong alkali solution, and under the physical cavitation effect of ultrasonic waves, the island-shaped coating layer that still firmly coats the surface of the lithium-rich manganese-based material is also difficult to be eroded and dissolved by substances such as HF in the electrolyte during the use of the battery, or to break under physical stress, etc., so that the basic structure of the product has relatively stable physical and chemical properties;

[0017] Coat a solid electrolyte layer on the surface of the carbon-coated lithium-rich manganese-based material:

[0018] By weight, take 100 - 110 parts of the carbon-coated lithium-rich manganese-based material, 6 - 8 parts of lithium hydroxide, 3 - 4 parts of titanium sulfate, 1 - 2 parts of lanthanum nitrate, and 0.8 - 1.2 parts of chromium sulfate;

[0019] Mix and disperse the carbon-coated lithium-rich manganese-based material and water to obtain a main material suspension with a concentration of 100 - 120 g / L;

[0020] Dissolve lithium hydroxide in water to obtain a lithium hydroxide solution with a mass fraction of 8 - 10%;

[0021] Add titanium sulfate, lanthanum nitrate, and chromium sulfate to water with a mass 10 - 15 times that of titanium sulfate, and stir to dissolve to obtain a mixed solution;

[0022] Add the mixed solution to the main material suspension, after mixing evenly, add the lithium hydroxide solution, heat and stir to react, keep warm and stand still, filter, wash, and dry, then under a nitrogen atmosphere, at a temperature of 700 - 750 °C, keep warm and react for 4 - 6 h, then cool and discharge to obtain the solid electrolyte and carbon composite-coated lithium-rich manganese-based cathode material.

[0023] On the basis of the island-like coating, the deposition of a coating layer with excellent lithium ion conductivity is further initiated. Specifically, under the action of the precipitant aluminum hydroxide and accompanied by a high-temperature calcination process, in the newly formed coating layer, lithium lanthanum titanium chromium oxide is mainly formed. On the basis of the island-like coating, the newly formed coating layer can use this as an "anchor point" and gradually fill the gaps between adjacent island-like coating layers. On the one hand, the surface of the lithium-rich manganese-based material gradually becomes smooth, the specific surface area is reduced, and the problem of excessive surface energy caused by too high specific surface area, such as the material dispersion problem during processing or the aggravation of surface side reactions, is prevented. At the same time, under the action of the anchor point, the new coating layer can also be firmly adsorbed and fixed on the surface, reducing the occurrence of shedding phenomenon. Finally, the composite coating layer on the surface has both excellent ionic conductivity and electronic conductivity and can be firmly adsorbed and fixed on the surface of the lithium-rich manganese-based material.

[0024] Furthermore, in the conductive carbon, it includes the following raw materials in parts by weight:

[0025] 30 - 40 parts of Super P, 8 - 10 parts of single-walled carbon nanotubes, 4 - 6 parts of graphene oxide.

[0026] Furthermore,

[0027] The D50 of the Super P is 40 - 50 nm;

[0028] The aspect ratio of the single-walled carbon nanotubes is 3500 - 4000, and its length is 4 - 6 μm;

[0029] The D50 of the graphene oxide is 300 - 350 nm;

[0030] The D50 of the lithium-rich manganese-based material is 3 - 5 μm.

[0031] In the above technical solution, by further combining different specifications of Super P, single-walled carbon nanotubes and graphene oxide in the coating layer material, the three can cooperate with each other to form a fast conductive network. The reason for choosing a part of graphene oxide for cooperation and its relatively large particles is that during its stacking process, on the one hand, gaps can be formed between particles, and on the other hand, there are also certain gaps inside its layered structure. During the battery expansion process, the existence of these gaps can play a good buffering role, thus avoiding the collapse of the surface structure.

[0032] Furthermore, the lithium-rich manganese-based material is spherical-like particles, and the sphericity of the lithium-rich manganese-based material is 8.6 - 8.8.

[0033] By further selecting a lithium-rich manganese-based material with a certain sphericity as the matrix, during the deposition process, it tends to form a uniform deposition layer, reducing excessive or insufficient deposition in local areas, thereby avoiding the presence of stress concentration areas on the surface and preventing the occurrence of local peeling problems.

[0034] Further, the ultrasonic reaction of the calcined material with a strong base solution includes:

[0035] Mix the calcined material and a strong base solution with a mass fraction of 2-4% according to a mass ratio of 1:8-10, and then carry out ultrasonic reaction for 10-15 minutes at a temperature of 40-60 °C and an ultrasonic frequency of 60-65 kHz;

[0036] Among them, the strong base solution is selected from any one of sodium hydroxide solution or potassium hydroxide solution.

[0037] Further, in the main material suspension, there is also acetylene black accounting for 2-4% of the mass of the lithium-rich manganese-based material, and the D50 of the acetylene black is 20-25 nm.

[0038] Further, in the main material suspension, there is also carboxymethyl cellulose accounting for 1.2-1.4% of the mass of the lithium-rich manganese-based material.

[0039] In addition, the inventor found that when further depositing on the surface of the lithium-rich manganese-based material, if a small amount of acetylene black is added to the main material suspension, it can assist in the deposition of the precursor of lithium lanthanum titanium chromium oxide on the surface of the lithium-rich manganese-based material, and moreover, it can also exist as a conductive agent in the lithium lanthanum titanium chromium oxide subsequently. Thus, the conductivity of the product is further improved;

[0040] The presence of a small amount of carboxymethyl cellulose is conducive to the firm deposition of the precursor on the surface, and during the subsequent anaerobic calcination process, it can gradually decompose and form a carbon skeleton, further enhancing the conductive performance and property stability of the product. Specific Embodiments

[0041] The following specific embodiments are used to further illustrate the present invention, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0042] Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0043] In the following examples and comparative examples, the lithium-rich manganese-based material used is xLi2MnO3·(1-x)LiNiO2, where x = 0.5;

[0044] Example 1

[0045] Carbon composite layer with island-like distribution coated on lithium-rich manganese-based material:

[0046] By weight, take 100 parts of absolute ethanol, 4 parts of glycerol, 4 parts of aluminum nitrate, 0.4 part of conductive carbon, and 38 parts of lithium-rich manganese-based material;

[0047] Among them, in the said conductive carbon, it includes raw materials with the following weight parts:

[0048] 30 parts of Super P, 8 parts of single-walled carbon nanotubes, 4 parts of graphene oxide;

[0049] The D50 of the said Super P is 40 nm;

[0050] The aspect ratio of the said single-walled carbon nanotubes is 3500, and its length is 4 μm;

[0051] The D50 of the said graphene oxide is 300 nm;

[0052] The D50 of the said lithium-rich manganese-based material is 3 μm;

[0053] The said lithium-rich manganese-based material is spherical-like particles, and the sphericity of the said lithium-rich manganese-based material is 8.6;

[0054] First, mix absolute ethanol and glycerol evenly, then add aluminum nitrate, stir and dissolve it, add conductive carbon, under the conditions of ultrasonic frequency of 100 kHz and temperature of 35 °C, ultrasonically disperse for 2 h, then add lithium-rich manganese-based material, and then under the conditions of temperature of 70 °C and stirring speed of 400 r / min, heat and stir to concentrate to volatilize absolute ethanol to obtain a concentrated material;

[0055] Transfer the concentrated material into a carbonization furnace, under the protection of nitrogen, heat and rise in temperature at a rate of 3 °C / min, at a temperature of 500 °C, continuously calcine for 4 h, then cool with the furnace to room temperature, and discharge to obtain a calcined material;

[0056] Mix the calcined material and a strong base solution with a mass fraction of 2% according to a mass ratio of 1:8, and under the conditions of temperature of 40 °C and ultrasonic frequency of 60 kHz, ultrasonically react for 10 min;

[0057] Among them, the said strong base solution is selected from sodium hydroxide solution;

[0058] After the ultrasonic reaction ends, wash with deionized water until the washing liquid is neutral, and dry to obtain carbon-coated lithium-rich manganese-based material;

[0059] Coat a solid electrolyte layer on the surface of the carbon-coated lithium-rich manganese-based material:

[0060] By weight, take 100 parts of carbon-coated lithium-rich manganese-based material, 6 parts of lithium hydroxide, 3 parts of titanium sulfate, 1 part of lanthanum nitrate, and 0.8 part of chromium sulfate;

[0061] After mixing the carbon-coated lithium-rich manganese-based material and water, ultrasonically disperse it for 45 min under the condition of an ultrasonic frequency of 65 kHz, then add acetylene black accounting for 2% of the mass of the lithium-rich manganese-based material and carboxymethyl cellulose accounting for 1.2% of the mass of the lithium-rich manganese-based material, and use a stirrer to stir and mix at a temperature of 65 °C and a rotation speed of 500 r / min for 60 min to obtain a main material suspension with a concentration of 100 g / L;

[0062] The D50 of the acetylene black is 20 nm;

[0063] Dissolve lithium hydroxide in water to obtain a lithium hydroxide solution with a mass fraction of 8%;

[0064] Add titanium sulfate, lanthanum nitrate, and chromium sulfate to water with a mass 10 times that of titanium sulfate, and stir to dissolve to obtain a mixed solution;

[0065] Add the mixed solution to the main material suspension, stir and mix at a rotation speed of 300 r / min with a stirrer for 30 min, then add the lithium hydroxide solution, and heat and stir to react for 2 h at a temperature of 80 °C and a stirring rotation speed of 600 r / min, keep warm and stand for 2 h, filter by suction, collect the filter cake, wash it 3 times with deionized water, dry it, then carry out a heat preservation reaction for 4 h at a temperature of 700 °C in a nitrogen atmosphere, cool it, and discharge it to obtain a solid electrolyte and carbon composite-coated lithium-rich manganese-based cathode material.

[0066] Example 2

[0067] Lithium-rich manganese-based material coated with an island-like distributed carbon composite layer:

[0068] By weight, take 110 parts of absolute ethanol, 5 parts of glycerol, 5 parts of aluminum nitrate, 0.5 part of conductive carbon, and 42 parts of lithium-rich manganese-based material;

[0069] Among them, in the conductive carbon, it includes the following raw materials in parts by weight:

[0070] 35 parts of Super P, 9 parts of single-walled carbon nanotubes, and 5 parts of graphene oxide;

[0071] The D50 of the Super P is 45 nm;

[0072] The aspect ratio of the single-walled carbon nanotubes is 3800, and its length is 5 μm;

[0073] The D50 of the graphene oxide is 320 nm;

[0074] The D50 of the lithium-rich manganese-based material is 4 μm;

[0075] The lithium-rich manganese-based material is spherical-like particles, and the sphericity of the lithium-rich manganese-based material is 8.7;

[0076] First, mix anhydrous ethanol and glycerol evenly, then add aluminum nitrate, stir and dissolve it, add conductive carbon, under the conditions of an ultrasonic frequency of 110 kHz and a temperature of 38 °C, ultrasonically disperse for 3 h, then add the lithium-rich manganese-based material, and then under the conditions of a temperature of 72 °C and a stirring speed of 400 r / min, heat and stir to concentrate to volatilize the anhydrous ethanol to obtain a concentrated material;

[0077] Transfer the concentrated material to a carbonization furnace, under the protection of nitrogen, heat and rise at a heating rate of 4 °C / min, under the condition of a temperature of 520 °C, continuously calcine for 5 h, then cool to room temperature with the furnace, and discharge to obtain a calcined material;

[0078] Mix the calcined material and a strong base solution with a mass fraction of 3% according to a mass ratio of 1:9, and under the conditions of a temperature of 50 °C and an ultrasonic frequency of 62 kHz, ultrasonically react for 12 min;

[0079] Among them, the strong base solution is selected from sodium hydroxide solution;

[0080] After the ultrasonic reaction is completed, wash with deionized water until the washing liquid is neutral, and dry to obtain a carbon-coated lithium-rich manganese-based material;

[0081] Coat a solid electrolyte layer on the surface of the carbon-coated lithium-rich manganese-based material:

[0082] By weight, take 105 parts of the carbon-coated lithium-rich manganese-based material, 7 parts of lithium hydroxide, 3 parts of titanium sulfate, 1.5 parts of lanthanum nitrate, and 0.9 part of chromium sulfate;

[0083] Mix the carbon-coated lithium-rich manganese-based material and water, ultrasonically disperse for 50 min under the condition of an ultrasonic frequency of 65 kHz, then add acetylene black accounting for 3% of the mass of the lithium-rich manganese-based material and carboxymethyl cellulose accounting for 1.3% of the mass of the lithium-rich manganese-based material, and use a stirrer to stir and mix for 60 min at a temperature of 68 °C and a speed of 500 r / min to obtain a main material suspension with a concentration of 110 g / L;

[0084] The D50 of the acetylene black is 22 nm;

[0085] Dissolve lithium hydroxide in water to obtain a lithium hydroxide solution with a mass fraction of 9%;

[0086] Add titanium sulfate, lanthanum nitrate, and chromium sulfate to water 12 times the mass of titanium sulfate, and stir and dissolve to obtain a mixed solution;

[0087] Add the mixed solution to the main material suspension, stir and mix at a speed of 300 r / min for 30 min using a stirrer, then add the lithium hydroxide solution, and heat and stir to react for 2 h at a temperature of 80 °C and a stirring speed of 600 r / min. Keep warm and stand for 2 h, then filter, collect the filter cake, wash it 4 times with deionized water, dry it, and then keep it warm and react for 5 h at a temperature of 720 °C in a nitrogen atmosphere, and then cool it and discharge it to obtain the solid electrolyte and carbon composite-coated lithium-rich manganese-based cathode material.

[0088] Example 3

[0089] Lithium-rich manganese-based material coated with an island-like distributed carbon composite layer:

[0090] Take 120 parts by weight of absolute ethanol, 6 parts of glycerol, 6 parts of aluminum nitrate, 0.6 part of conductive carbon, and 45 parts of lithium-rich manganese-based material;

[0091] Among them, in the said conductive carbon, it includes the following raw materials in parts by weight:

[0092] 40 parts of Super P, 10 parts of single-walled carbon nanotubes, 6 parts of graphene oxide;

[0093] The D50 of the said Super P is 50 nm;

[0094] The aspect ratio of the said single-walled carbon nanotubes is 4000, and its length is 6 μm;

[0095] The D50 of the said graphene oxide is 350 nm;

[0096] The D50 of the said lithium-rich manganese-based material is 5 μm;

[0097] The said lithium-rich manganese-based material is spherical-like particles, and the sphericity of the said lithium-rich manganese-based material is 8.8;

[0098] First, mix absolute ethanol and glycerol evenly, then add aluminum nitrate, stir and dissolve it, then add conductive carbon, and under the conditions of an ultrasonic frequency of 120 kHz and a temperature of 40 °C, ultrasonically disperse for 4 h, then add the lithium-rich manganese-based material, and then heat and stir to concentrate at a temperature of 75 °C and a stirring speed of 400 r / min to volatilize the absolute ethanol and obtain a concentrated material;

[0099] Transfer the concentrated material to a carbonization furnace, heat and raise the temperature at a rate of 5 °C / min under a nitrogen protection state, and continuously calcine at a temperature of 550 °C for 6 h, then cool it to room temperature with the furnace and discharge it to obtain a calcined material;

[0100] Mix the calcined material and a strong base solution with a mass fraction of 4% according to a mass ratio of 1:10, and then ultrasonically react for 15 min at a temperature of 60 °C and an ultrasonic frequency of 65 kHz;

[0101] Among them, the strong base solution is selected from potassium hydroxide solution;

[0102] After the ultrasonic reaction is completed, wash with deionized water until the washing liquid is neutral, and then dry to obtain the carbon-coated lithium-rich manganese-based material;

[0103] Coat a solid electrolyte layer on the surface of the carbon-coated lithium-rich manganese-based material:

[0104] By weight, take 110 parts of the carbon-coated lithium-rich manganese-based material, 8 parts of lithium hydroxide, 4 parts of titanium sulfate, 2 parts of lanthanum nitrate, and 1.2 parts of chromium sulfate;

[0105] Mix the carbon-coated lithium-rich manganese-based material and water, and ultrasonically disperse for 60 min under the condition of an ultrasonic frequency of 65 kHz. Then add acetylene black accounting for 4% of the mass of the lithium-rich manganese-based material and carboxymethyl cellulose accounting for 1.4% of the mass of the lithium-rich manganese-based material. Stir and mix for 60 min with a stirrer at a temperature of 70 °C and a rotation speed of 500 r / min to obtain a main material suspension with a concentration of 120 g / L;

[0106] The D50 of the acetylene black is 25 nm;

[0107] Dissolve lithium hydroxide in water to obtain a lithium hydroxide solution with a mass fraction of 10%;

[0108] Add titanium sulfate, lanthanum nitrate, and chromium sulfate to water 15 times the mass of titanium sulfate, and stir to dissolve to obtain a mixed solution;

[0109] Add the mixed solution to the main material suspension, stir and mix at a rotation speed of 300 r / min with a stirrer for 30 min, then add the lithium hydroxide solution, and heat and stir to react for 2 h at a temperature of 80 °C and a stirring rotation speed of 600 r / min. Keep warm and stand for 2 h, filter by suction, collect the filter cake, wash it 5 times with deionized water, dry it, then carry out a heat preservation reaction for 6 h at a temperature of 750 °C in a nitrogen atmosphere, cool it, and discharge to obtain the solid electrolyte and carbon composite-coated lithium-rich manganese-based positive electrode material.

[0110] Example 4

[0111] Compared with Example 1, the difference in this example is that graphene oxide is not added to the conductive carbon, and the other conditions remain unchanged.

[0112] Example 5

[0113] Compared with Example 1, the difference in this example is that the D50 of graphene oxide is 60 nm, and the other conditions remain unchanged.

[0114] Example 6

[0115] Compared with Example 1, this example is different in that the sphericity of the lithium-rich manganese-based material is 8.4, and the remaining conditions remain unchanged.

[0116] Example 7

[0117] Compared with Example 1, this example is different in that no acetylene black is added, and the remaining conditions remain unchanged.

[0118] Comparative Example 1

[0119] Compared with Example 1, this comparative example is different in that:

[0120] The lithium-rich manganese-based material is coated with a continuously distributed carbon composite layer:

[0121] By weight, take 100 parts of absolute ethanol, 4 parts of glycerol, 4 parts of aluminum nitrate, 0.4 part of conductive carbon, and 38 parts of lithium-rich manganese-based material;

[0122] Among them, in the said conductive carbon, it includes raw materials in the following weight parts:

[0123] 30 parts of Super P, 8 parts of single-walled carbon nanotubes, 4 parts of graphene oxide;

[0124] The D50 of the said Super P is 40 nm;

[0125] The aspect ratio of the said single-walled carbon nanotubes is 3500, and its length is 4 μm;

[0126] The D50 of the said graphene oxide is 300 nm;

[0127] The D50 of the said lithium-rich manganese-based material is 3 μm;

[0128] The said lithium-rich manganese-based material is spherical-like particles, and the sphericity of the lithium-rich manganese-based material is 8.6;

[0129] First, mix absolute ethanol and glycerol evenly, then add aluminum nitrate, stir and dissolve it, then add conductive carbon, under the conditions of ultrasonic frequency of 100 kHz and temperature of 35 °C, ultrasonically disperse for 2 h, then add the lithium-rich manganese-based material, and then under the conditions of temperature of 70 °C and stirring speed of 400 r / min, heat and stir to concentrate to volatilize the absolute ethanol to obtain a concentrated material;

[0130] Transfer the concentrated material into a carbonization furnace, under the protection of nitrogen, heat and rise at a heating rate of 3 °C / min, at a temperature of 500 °C, continuously calcine for 4 h, then cool with the furnace to room temperature, and discharge to obtain a calcined material, which is the carbon-coated lithium-rich manganese-based material.

[0131] The remaining conditions remain unchanged.

[0132] The products obtained from the above-mentioned examples and comparative examples were subjected to performance tests. The specific test methods and test results are as follows:

[0133] Weigh LLMO, acetylene black, and PVDF in a mass ratio of 8:1:1 and dry grind them for 6 minutes. Then, drop an appropriate amount of N-methylpyrrolidone into the grinding material until it becomes viscous. Coat it evenly on a 12-μm aluminum foil and place it in a vacuum drying oven at 110 °C for 6 hours. Use a tablet press to punch the dried electrode sheet into a circular sheet with a pore diameter of 12 mm, and assemble it into a CR2025 coin cell in a glove box with a positive and negative electrode case, a Celgard-2500 polypropylene microporous separator, a nickel mesh current collector, and an electrolyte composed of 1 mol / L LiPF6 dissolved in EC+DMC+DMC (volume ratio 1:1:1). Perform charge-discharge tests on a Neware CT-4008 constant-temperature battery test system at a temperature of 25 °C.

[0134] First, at a 0.1C rate, the initial discharge capacity of the battery was tested;

[0135] Then, within the working voltage range of 2.0V - 4.5V, corresponding charge-discharge tests were carried out;

[0136] Charge-discharge tests were carried out at 1C and 3C rates respectively, and the capacity retention rate after 150 cycles was tested. The detailed test results are shown in Table 1;

[0137] Table 1: Product performance test results

[0138]

[0139] It can be seen from the test results in Table 1 that the products obtained by the present invention have good capacity performance and a high capacity retention rate during high-rate charge and discharge.

[0140] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A synthesis method of a solid electrolyte and carbon composite-coated lithium-rich manganese-based cathode material, characterized in that, The specific synthesis steps are as follows: Coating the lithium-rich manganese-based material with an island-like distributed carbon composite layer: Take 100 - 120 parts by weight of absolute ethanol, 4 - 6 parts of glycerol, 4 - 6 parts of aluminum nitrate, 0.4 - 0.6 parts of conductive carbon, and 38 - 45 parts of lithium-rich manganese-based material; First, mix absolute ethanol and glycerol evenly, then add aluminum nitrate, stir to dissolve, add conductive carbon, ultrasonically disperse evenly, and then add the lithium-rich manganese-based material, heat and stir to concentrate to volatilize the absolute ethanol to obtain a concentrated material; Transfer the concentrated material into a carbonization furnace, under nitrogen protection, at a temperature of 500 - 550 °C, continuously calcine for 4 - 6 h, then cool and discharge to obtain a calcined material; Ultrasonically react the calcined material with a strong alkali solution, wash with water, and dry to obtain the carbon-coated lithium-rich manganese-based material; Coating a solid electrolyte layer on the surface of the carbon-coated lithium-rich manganese-based material: Take 100 - 110 parts by weight of the carbon-coated lithium-rich manganese-based material, 6 - 8 parts of lithium hydroxide, 3 - 4 parts of titanium sulfate, 1 - 2 parts of lanthanum nitrate, and 0.8 - 1.2 parts of chromium sulfate; Mix and disperse the carbon-coated lithium-rich manganese-based material and water to obtain a main material suspension with a concentration of 100 - 120 g / L; Dissolve lithium hydroxide in water to obtain a lithium hydroxide solution with a mass fraction of 8 - 10%; Add titanium sulfate, lanthanum nitrate, and chromium sulfate to water with a mass 10 - 15 times that of titanium sulfate, stir to dissolve to obtain a mixed solution; Add the mixed solution to the main material suspension, mix evenly, then add the lithium hydroxide solution, heat and stir to react, keep warm and stand still, filter, wash, and dry, then under a nitrogen atmosphere, at a temperature of 700 - 750 °C, keep warm and react for 4 - 6 h, then cool and discharge to obtain the solid electrolyte and carbon composite-coated lithium-rich manganese-based cathode material.

2. The synthesis method of a solid electrolyte and carbon composite-coated lithium-rich manganese-based cathode material according to claim 1, characterized in that, In the conductive carbon, it includes the following raw materials in parts by weight: 30 - 40 parts of Super P, 8 - 10 parts of single-walled carbon nanotubes, and 4 - 6 parts of graphene oxide.

3. The synthesis method of a solid electrolyte and carbon composite-coated lithium-rich manganese-based cathode material according to claim 2, characterized in that The D50 of the Super P is 40 - 50 nm; The aspect ratio of the single-walled carbon nanotubes is 3500 - 4000, and its length is 4 - 6 μm; The D50 of the graphene oxide is 300 - 350 nm; The D50 of the lithium-rich manganese-based material is 3 - 5 μm.

4. The synthesis method of a solid electrolyte and carbon composite-coated lithium-rich manganese-based cathode material according to claim 3, characterized in that, The lithium-rich manganese-based material is spherical-like particles, and the sphericity of the lithium-rich manganese-based material is 8.6 - 8.

8.

5. The synthesis method of a solid electrolyte and carbon composite-coated lithium-rich manganese-based cathode material according to claim 1, characterized in that, The ultrasonic reaction of the calcined material with a strong alkali solution includes: Mix the calcined material and a strong alkali solution with a mass fraction of 2 - 4% according to a mass ratio of 1:8 - 10, and under a temperature of 40 - 60 °C and an ultrasonic frequency of 60 - 65 kHz, ultrasonically react for 10 - 15 min; Among them, the strong alkali solution is selected from any one of sodium hydroxide solution or potassium hydroxide solution.

6. The synthesis method of a solid electrolyte and carbon composite-coated lithium-rich manganese-based cathode material according to claim 1, wherein In the main material suspension, it also includes acetylene black accounting for 2 - 4% of the mass of the lithium-rich manganese-based material, and the D50 of the acetylene black is 20 - 25 nm.

7. The synthesis method of a solid electrolyte and carbon composite-coated lithium-rich manganese-based cathode material according to claim 1, characterized in that, In the main material suspension, carboxymethyl cellulose accounting for 1.2-1.4% of the mass of the lithium-rich manganese-based material is further included.

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